In order to connect tubular molded parts made of a synthetic material, welding sleeves are used as a rule. These sleeves have a heating element. By supplying electrical heating energy the heating element is heated and the sleeve is welded with the tubular molded part. In this way, a wide variety of molded parts in pipeline systems are connected together. The energy necessary for the welding process is supplied from a welding device. These devices are designed such that a variety of welding programs are stored for different molded parts and release the energy respectively required for the molded part to be welded. The energy required depends on the material, the type and the size of the molded part. The required welding time is also controlled by the molded part parameters. For example, the welding time required during the welding of pipes, while using a heater coil welding sleeve with a nominal diameter of 63 mm amounts to approximately 2 min. In the case of larger pipe dimensions, the welding time increases correspondingly. During this time, no additional welding with the welding device can take place. However, on the construction site, a multitude of such weldings must often be carried out simultaneously. Since the welding operations must take place in succession, this process requires a great deal of time.
The known welding devices are designed in such a way that in the case of new molded parts, the changed parameters, for example, dimension or material, which require changed welding parameters, can no longer be programmed into the welding device at a later time. For this reason, different welding devices are required for different molded part categories.